Boron and chlorine concentrations in geological standards and in representative volcanic rock samples were determined by prompt gamma activation analysis (PGAA). The results of the GSJ standard measurements proved the high precision of PGAA in measuring the boron, chlorine, other trace elements (Sc, Nd, Sm, and Gd) and the major element contents of the samples. The rock samples originate from the western part of the Northern-Pannonian Volcanic Field (NPVF), which includes the Central Slovakian Volcanic Field (CSVF), the Börzsöny and the Visegrád Mts. (VMt.). The oldest 16-13.5 Ma samples as the first products of the Miocene calc-alkaline volcanism are the most enriched in B (11-29 μg/g), whereas the primitive basaltic andesites (from CSVF), the latest products (9 Ma) of the volcanic activity have lower B content (8-9 μg/g). The measured B concentrations correlate positively with fluid-mobile elements, and the trace element pattern of the samples show subduction related signatures. The chlorine content of the investigated samples shows wide variation between 42.62 and 1148.45 μg/g. The 9 Ma samples from the CSVF show Cl contents between 150-160 μg/g. In agreement with the latest geodynamic models of the Neogene calc-alkaline volcanism1,2 in the NPVF during the shallow, prograding subduction, the fluid-mobile elements metasomatized the mantle wedge. Thus the oldest volcanic rocks have relatively higher B (>11 μg/g) and high but variable Cl contents. As the subduction waned and extension proceeded, the magma generation region changed to a not thoroughly metasomatized mantle by the former subduction event, resulting in lower B, low and stable Cl content of the younger (9 Ma) volcanic rocks.
ASJC Scopus subject areas
- Analytical Chemistry
- Nuclear Energy and Engineering
- Radiology Nuclear Medicine and imaging
- Public Health, Environmental and Occupational Health
- Health, Toxicology and Mutagenesis